Iron-based metal-organic frameworks as novel platforms for catalytic ozonation of organic pollutant: Efficiency and mechanism.

Developing new heterogeneous catalysts has attracted much attention and is of significant importance for the efficient catalytic ozonation of organic pollutant. Herein, for the first time, we explored four environmental-benign iron-based MOFs (Fe-MOFs) for the catalytic ozonation reaction. These Fe-MOFs were characterized by PXRD, FT-IR, SEM, XPS, N2 sorption-desorption isotherms and chemisorbed-pyridine IR. All Fe-MOFs show high catalytic performances with their intrinsic Lewis acid sites (LAS). Furthermore, MIL-53(Fe) demonstrates the highest catalytic activity because of its largest amount of LAS and suitable porosity-derived attractive mass-transfer property. The Rhodamine B (RhB) degradation kinetic rate is calculated to be 5.76 min-1 with MIL-53(Fe), while 1.82 min-1 with MIL-88B(Fe), 1.40 min-1 with MIL-101(Fe), 0.87 min-1 with MIL-100(Fe) and 0.43 min-1 of ozonation alone. The TOC removal in MIL-53(Fe)/O3 system is 4 times higher than that of ozonation alone. MIL-53(Fe) displays acceptable reusability and stability after 5 cycles. Surface LAS of MIL-53(Fe) are the active sites for the ozone decomposition. Moreover, surface-adsorbed hydroxyl radical, superoxide radical and singlet oxygen are confirmed as the reactive oxygen species from ozone decomposition in MIL-53(Fe) suspension. This work offers new platforms for catalytic ozonation and may drive the development of MOFs-based catalytic ozonation for effective water treatment.